The present invention relates to a filter assembly having a primary and secondary filter incorporated therein that provides for continuous fluid flow through the filter assembly, even though the primary filter may have become obstructed by contaminants removed from the fluid medium.
It has been recognized that it is necessary in many instances to provide for a continuous flow of a fluid that passes through a filtering device, even after the filtering device has become clogged through extensive use thereof. Examples of such use of fluid filter devices in the prior known filtering systems are illustrated in the U.S. Pat. No. 3,262,565 to Silverwater; U.S. Pat. No. 3,283,902 to Farris et al; U.S. Pat. No. 4,038,189 to Dison et al; and U.S. Pat. No. 4,885,082 to Cantoni. All of the prior filter devices as illustrated in the aforesaid patents include dual filter systems that were designed to permit flow of the fluid medium to be filtered to continue even though the primary filter may have become obstructed in the use thereof. These prior known systems, particularly as illustrated in the Silverwater and Farris et al Patents, included concentrically located filters that were disposed in a cylindrical housing, and also included a relief valve construction that was responsive to back pressure caused by obstruction of the primary filter. However, the prior systems were somewhat complex and unreliable in use. Further, these prior known devices included a number of elements that had to be precisely interfitted which rendered the filter assemblies uneconomical in use.
Other systems as represented by the prior art of which applicant is aware but that are of only general interest, are shown in the U.S. Pat. No. 2,879,892 to Frakes; U.S. Pat. No. 3,591,002 to Rosaen; U.S. Pat. No. 3,950,248 Brown et al; and U.S. Pat. No. 4,423,751 Roettgen.
As will be described hereinafter, the subject invention includes a relatively simple dual filter system that not only provides for the efficient filtering of the fluid medium as required, but that insures continuous flow of the fluid through a by-pass filter system when the primary filter becomes obstructed. The subject invention also includes a simple alarm device that audibly and visually indicates when the primary filter system has become obstructed.